The invention relates to an article used as a filament storage device to facilitate filament positioning during modification of a filament. More particularly the invention provides a filament organizer including a detachable positioner for conveniently handling an accessory to be attached to a filament, especially an optical fiber to produce a functional optical device. Such a device includes a temperature compensated optical fiber Bragg grating that may be precisely tuned to a prescribed wavelength using a tuning apparatus according to the present invention.
Technological advancements, particularly in telecommunications, have caused a migration from systems and devices based upon electronics to those that integrate electronics with optics. These systems and related devices are known collectively as optoelectronics. The movement of signals using photons instead of electrons provides advantages of speed, information-carrying capability, immunity from interference, lower cost, and higher reliability.
Growth of optoelectronic systems occurs as phone companies increasingly promote the use of fiber-optic cable and related devices for developing ever-expanding telecommunications networks. Success in telecommunications markets has produced a demand for innovations in fiber-optic technology. Increasing demand for products typically translates into a need to accelerate the output rate and assembly of products and systems desired by consumers. Acceleration of output rates depends upon efficiency in manufacturing operations, usually through process automation.
Methods used currently for assembly and testing of optoelectronic systems and devices are largely manual and time consuming. This applies particularly to processes for introducing special features such as periodic refractive index gratings into optical fibers. Formation of a refractive index grating, or Bragg grating, into an optical fiber requires a number of steps for manually handling lengths of optical fiber during a series of manufacturing operations.
A optical fiber Bragg grating provides a periodic variation of refractive index within a length of an optical fiber. The grating may be formed or written during exposure of a photosensitive optical fiber to an appropriate pattern of ultraviolet radiation. Applications for Bragg gratings exist in telecommunications systems to control the wavelength of laser light, to introduce dispersion compensation, for example. The characteristics of Bragg gratings change with changes of strain and temperature. A change in temperature will change the wavelength of light transmitted via a Bragg grating, with undesirable consequences. One solution to this problem is the use of a temperature compensating structure attached to the portion of an optical fiber containing the Bragg grating. This is usually accomplished by clamping a Bragg grating containing optical fiber, under tension, into a mechanical structure combining a low expansion material with a high expansion material. This method of passive temperature compensation is well known as a means for improving wavelength stability of optical fiber Bragg gratings. U.S. Pat. No. 5,042,898 discloses an apparatus for temperature compensation of a fiber Bragg grating comprising two juxtaposed compensating members with the required differences in thermal expansion. The apparatus applies either tensile or compressive stress to the grating. Other references addressing temperature compensation of optical fiber Bragg gratings, using fiber length variation, include United States Patents U.S. Pat. No. 5,991,483, U.S. Pat. No. 6,101,301 and WIPO publication WO 98/59267. Japanese publication JP 9211348 describes the use of a piezoelectric transducer to modulate the strain in a fiber in response to electrical signals. Such devices are effective but costly.
Temperature compensated optical fiber Bragg grating packages, as previously discussed, are typically large, exhibiting variation of reflection wavelength from one package to another. In some cases, the design of temperature compensating structures is complex requiring multiple points of connection to form a package having a negative coefficient of thermal expansion. Some temperature compensated packages include fine adjustment of the grating wavelength but this may involve complicated procedures such as the extension or compression of the total package as described in WO 98/59267.
Regardless of the availability of solutions for compensating the temperature drift of optical fiber Bragg gratings, little has been revealed for automating processes either for forming Bragg gratings or attaching structures or accessories to optical fibers to perform a desired function such as temperature compensation. With increasing demand for optoelectronic systems there is a need to improve optical fiber handling to achieve more cost effective production of large quantities of optical fiber devices.
The present invention satisfies the need for effective and compact handling of filamentary materials during manufacturing operations including process steps that include attaching accessories to a filament and producing structural and related changes in the filament. When applied to optical fibers, an article, also described herein as a filament organizer, provides compact containment of an optical fiber during the writing of an optical fiber Bragg grating and further processing to provide a temperature compensated optical fiber Bragg grating package. Preferably the filament organizer includes a detachable accessory positioner. The filament organizer allows relatively precise positioning of at least a section of optical fiber to facilitate attachment of accessories, such as thermal compensators, held temporarily in an accessory cradle of an accessory positioner.
An accessory positioner, adapted for variable positioning in a filament organizer, conveniently allows placement of an accessory in the accessory cradle when there is a spaced relationship between the accessory positioner and a filament, preferably an optical fiber. Using suitable means to move the accessory positioner in the filament organizer, an accessory may be moved towards a filament with precise alignment of the two before joining them together. Means to facilitate movement of an accessory positioner between positions include sliding motion on e.g. racks, or tracks or movement based upon the use of bearings, bars, hinges, cams and the like.
A filament organizer according to the present invention may be used to assemble filamentary devices, particularly devices including optical fibers. An example of such use involves either changing the inherent characteristics of an optical fiber or incorporating an optical fiber into a functional assembly. The inherent characteristics of an optical fiber change with adjustment of its refractive index properties, as in the formation of a variety of fiber Bragg gratings. Incorporation of an optical fiber into a functional assembly provides useful devices such as temperature compensated fiber Bragg gratings. Refractive index changes and functional assembly production, according to the present invention, use a filament organizer during the formation of a temperature compensated optical fiber Bragg grating. Thereafter an optical fiber Bragg grating may be precisely tuned using an accessory positioner with a tuning jig according to the present invention.
More particularly, the present invention provides a filament organizer for attaching an accessory to a section of filament. The filament organizer comprises a frame including a plurality of guides. Also, the filament organizer includes an accessory positioner adapted for sliding engagement with the frame between a first position and a second position. The accessory positioner includes a first spool and a second spool having a filament extended between them to pass around the guides. This locates the section of filament for attachment of an accessory. An accessory cradle, included with the accessory positioner, receives an accessory in the first position to transport it to the second position from which the accessory is attached to the section of filament.
An accessory positioner according to the present invention preferably comprises a support having a forward edge and a first surface opposite a second surface. The support further includes a first hub having separation from a second hub. A first spool, engaging the first hub, is mounted for rotation on the support. The accessory positioner also includes a second spool, engaging the second hub, mounted for rotation on the support. A separation exists from the first spool to the second spool for suspension of a section of filament between the two to locate the section of filament before attaching an accessory to the filament. The accessory positioner further has an accessory cradle to receive an accessory to be attached to the section of filament.
A preferred embodiment of an accessory positioner may be used for attaching an accessory to a section of a filament when the accessory positioner is mounted in a substantially rectangular frame that includes a plurality of forward guides and a plurality of rear guides. In this case the accessory positioner moves in sliding engagement with the frame. The movable accessory positioner has a first surface opposite a second surface, a front edge and a rear edge. A first spool occupies a position adjacent to the first surface, between the front edge and the rear edge. A second spool also lies adjacent to the first surface between the front edge and the rear edge. The use of a filament restrictor transmits a force to each of the first spool and the second spool to apply tension to a filament extended therebetween. The filament passes around the rear guides and the forward guides to locate a section of filament between the forward guides. A movable accessory positioner also has an accessory cradle at its front edge to move from a retracted position to a proximate position relative to a filament. The accessory cradle, in the retracted position receives a accessory for placement in axial alignment with the section of filament when the accessory cradle moves into the proximate position to attach the accessory to the section of filament.
Accessory attachment according to the present invention preferably uses an attachment fixture for arranging at least one filament organizer for attaching an accessory to a filament. The attachment fixture comprises a base plate that includes at least one organizer slot and has a first end and a second end. A first support is secured to the first end of the base plate and a second support is secured to the second end of the base plate. At least one rod extends between the first support and the second support so that the rod contacts a filament organizer positioned in an organizer slot.
A Bragg grating may be tested or optically proofed according to the present invention using an optical proofing fixture for arranging a plurality of accessory positioners for organizing optical fiber pigtail ends to monitor light passing between the pigtail ends. The optical proofing fixture comprises a first faceplate, and a second faceplate. At least one support bar connects the first faceplate to the second faceplate. Each of a plurality of pigtail mounts, coupled between the first faceplate and the second faceplate, includes a resilient grip having a grip retention slit to releasably retain pigtail ends of an optical fiber. The optical proofing fixture further includes a flange connected between the first faceplate and the second faceplate.
The present invention includes a tuning apparatus for precise adjustment of the wavelength of a refractive index grating, formed in a section of optical fiber. The tuning apparatus comprises a pair of spaced-apart cantilever arms having the section of optical fiber suspended between them. A clamp immobilizes the section of optical fiber to allow a tuning blade to apply force to at least one of the pair of cantilever arms. An actuator connected to the tuning blade has a controller for moving the tuning blade under a prescribed force and distance causing displacement of the cantilever arm. This increases the separation between the pair of cantilever arms, thereby changing the length of the section of optical fiber and adjusting the wavelength of a refractive index grating formed in the optical fiber.
The present invention further includes a process for attaching an accessory to a filament, preferably in the form of an optical fiber. The process comprises the steps of providing a filament held in a filament organizer. A filament organizer comprises a frame including a plurality of guides and an accessory positioner mounted on the frame for movement between a first position and a second position. The accessory positioner includes a first spool and a second spool having a filament extended between them to pass around the guides to locate a section of filament for attachment of an accessory. The accessory positioner further has an accessory cradle to receive the accessory, in the first position, for transportation of the accessory to the second position for attachment to the section of filament. An accessory may be placed in the accessory cradle when the accessory positioner is in the first position. The accessory has a pair of spaced apart cantilever arms, each including a contact point. Moving the accessory positioner into the second position places the section of filament adjacent to the accessory to contact the contact points for bonding the accessory to the section of filament at each of the contact points.
An attachment fixture may be used during attachment of the filament to the accessory, at its contact points. The fixture facilitates processing of a plurality of filament organizers at the same time. An attachment fixture comprises a base plate including a plurality of organizer slots and having a first end and a second end. A first support is secured to the first end and a second support is secured to the second end. The fixture includes at least one rod extending between the first support and the second support to contact each of the plurality of filament organizers positioned in each of the plurality of organizer slots. A rod may be made of a conducting material that acts as a heating element to assist with elevated temperature bonding of a filament to contact points of the accessory.
The term xe2x80x9cfilamentxe2x80x9d as used herein refers to a threadlike structure particularly an optical fiber and related optical waveguides, including those having a refractive index grating or Bragg grating formed therein.
The term xe2x80x9cthermal compensatorxe2x80x9d means an accessory for attachment to a filament, particularly an optical fiber that includes a Bragg grating, to provide a temperature compensated Bragg grating, which maintains a target wavelength independent of temperature variation.
The term xe2x80x9cfilament organizerxe2x80x9d refers to an article for convenient containment and handling of extended lengths of filament, particularly optical fiber, during processing. A filament organizer according to the present invention includes a movable mini-tray as an accessory positioner.
The term xe2x80x9caccessory positionerxe2x80x9d describes a movable, detachable portion of a filament organizer. An accessory positioner includes at least a pair of spaced-apart spools for holding a filament and to allow access to a section of filament during processing of a filament.
The term xe2x80x9ctuning jigxe2x80x9d refers to a device used for adjusting a temperature compensated optical fiber Bragg grating to a target, tuned wavelength.
The term xe2x80x9cattachment fixturexe2x80x9d is used to describe an apparatus that may be used with one or more filament organizers to facilitate attachment of an accessory to a filament.
The term xe2x80x9cproofingxe2x80x9d applies to a filament in the form of an optical fiber containing a Bragg grating and means the process of monitoring optical properties during thermal cycling to confirm attainment of target values of e.g. optical fiber Bragg grating wavelength response within a prescribed temperature range.
The term xe2x80x9cproofing fixturexe2x80x9d refers to an apparatus that may be used with one or more accessory positioners during proofing and related evaluation of the properties of one or more optical fiber Bragg gratings.
The term xe2x80x9ctensionerxe2x80x9d or xe2x80x9cfilament restrictorxe2x80x9d describes a device or structure used with a filament containment assembly, e.g. a pair of spools, to restrain a filament so that it does not become slack.
The term xe2x80x9cfiber tensioningxe2x80x9d refers to the process of attaching a weight or applying tension to a section of filament to place the filament under strain. Fiber tensioning of an optical fiber precedes fiber-modifying operations such as the writing of a Bragg grating in the fiber and attachment of a thermal compensator to the optical fiber.
The term xe2x80x9ccoupledxe2x80x9d indicates the existence of intervening parts in an attachment structure.